HHVM is an interesting data point too - kept PHP compatibility for as long as there were significant open-source users (eg wikipedia), but after PHP7 caught up with a lot of the performance gains, meaning there was little reason to use HHVM in PHP-compatibility mode, they then went off in their own direction with Hacklang (which is still actively developed) to get all the benefits of being PHP-like without the drawbacks of being PHP-compatible.
PHP has some benefits to its design that the vast majority of other languages don’t — deployment is as simple as “stick a .php file on in your website folder”, hitting the “refresh” button gets you the latest code with no “build” or “restart server” step, it’s all stateless shared-nothing so you won’t have data from one request changing the behaviour of another request, etc.
But the implementation has a lot of drawbacks - the language is painful, typing is bolted-on and still incomplete after years of work (eg there are no typed arrays), the standard library is an inconsistent mess thanks to its origins of “take several other language’s standard libraries and duct-tape them together”, etc.
“PHP-like but incompatible” isn’t in itself a useful feature — it is the thing which unlocks a bunch of useful features (a sensible standard library, sensible list/dict datatypes, typed collections, XHP, async functions, generics)
Overall, I'm glad they do these things, though since it is better to have this code accessible than absent. Good on them!